The present invention relates to a method of attaching a sheet filter to the inlet opening (a discharging hole viewing from the room to be ventilated) of a ventialtion fan or a range hood.
Since a ventilation fan or a range hood sucks steam, dust, and oily substance, etc. from its ambient atmosphere and, as a result, it gets extremely dirty and makes itself very difficult to clean, there has been a practice to attach a filtering device (generally called a ventilation fan cover or a range hood cover) having with a filter made of nonwoven fabric at the inlet opening of said ventilation fan or said range hood so as to catch the oily substance, steam, etc. which are included in the air sucked by said filtering device.
Such a filtering device, as stated in Japanese Utility Model notification No. 56-18908, Japanese Utility Model laid open No. 52-167660, Japanese Utility Model laid open No. 56-149837, or Japanese Utility Model laid open No. 59-195436, consists of a frame made of synthetic resin or metal, a filter made of nonwoven fabric which covers the above-mentioned inlet opening together with said frame from outside, and means to set temporarily said filter to said frame and, when the filter gets dirty with oil, steam, etc., only the filter is replaced.
However the frame of such a filtering device must be cleaned at proper intervals because it gets dirty with oily smoke, etc. and, moreover, the replacement of said filtering device is troublesome because the filter must be attached to said frame before attaching the filtering device to the inlet opening. Especially in the case of a range hood, it is extremely difficult to manufacture a filtering device according to an individual range hood because there are range hoods of a hundred of sizes and shapes.
Though there in the market are ventilation fan covers consisting of a frame made of press-formed aluminum or vinyl chloride sheet and to which nonwoven fabric or other material is bonded, there has been a problem that such covers bring a high cost because the nonwoven fabric must be disposed together with said frame when they get dirty by use, and there has been a further problem that extremely various kinds of covers must be manufactured to suit with respective ventilation fans and range hoods.